To prevent deterioration of the image density and the resolution of toner and occurrence of fog and to enhance transfer efficiency.

These ferrite particles 1 containing the ammonium salt type charge controller are prepared by uniformly mixing ferrite 2 and an ammonium salt 3 acting as the charge controller and attaching the ammonium salt 3 to the ferrite 2 in one body to form each fine particles 1 each having an average diameter of ≤1.0 μm. Since the ferrite 2 and the ammonium salt 3 are mixed uniformly, the ammonium salt 3 is dispersed into the toner uniformly and the ammonium salt 3 does not condense with each other and the uneven charge on the toner is not generated.